The present invention relates to disc drive data storage systems and, more particularly, to a disc drive data storage system having a slider which has a flying height that is relatively insensitive to changes in altitude.
Disc drives of the xe2x80x9cWinchesterxe2x80x9d type are well known in the industry. Such drives use rigid discs which are coated with a magnetizable medium for storage of digital information in a plurality of circular, concentric data tracks. The discs are mounted on a spindle motor which causes the discs to spin and the surfaces of the discs to pass under respective hydrodynamic (e.g. air) bearing disc head sliders. The sliders carry transducers which write information to and read information from the disc surfaces.
An actuator mechanism moves the sliders from track-to-track across the surfaces of the discs under control of electronic circuitry. The actuator mechanism includes a track accessing arm and a suspension for each head gimbal assembly. The suspension includes a load beam and a gimbal. The load beam provides a load force which forces the slider toward the disc surface. The gimbal is positioned between the slider and the load beam, or is integrated in the load beam, to provide a resilient connection that allows the slider to pitch and roll while following the topography of the disc.
The slider includes an air bearing surface which faces the disc surface. As the disc rotates, the disc drags air under the slider and along the air bearing surface in a direction approximately parallel to the tangential velocity of the disc. As the air passes beneath the air bearing surface, air compression along the air flow path causes the air pressure between the disc and the air bearing surface to increase which creates a hydrodynamic lifting force that counteracts the load force and causes the slider to lift and fly above or in close proximity to the disc surface.
One type of slider is a xe2x80x9cself-loadingxe2x80x9d air slider, which includes a leading taper, a pair of raised side rails, a cavity dam and a subambient pressure cavity. The leading taper is lapped onto the end of the slider that is opposite to the recording head. The leading taper pressurizes the air as the air is dragged under the slider by the disc surface. The cavity dam provides an expansion path for the air to de-pressurize as it is dragged into the sub-ambient pressure cavity by the disc velocity. The expanded air in the cavity provides a self-loading force which forces the slider toward the disc surface. The counteraction between positive pressure developed along the side rails, the preload force provided by the suspension and the self-loading force provides the air bearing with a high vertical stiffness.
The physical separation between the slider and the disc surface at the recording head is an important parameter to disc drive performance. It is desired to minimize variation in the head clearance or xe2x80x9cflying heightxe2x80x9d as the data storage device is operated at different altitudes above sea level. Such variation in flying height normally occurs in state-of-the-art air bearings as a result of changes in ambient pressure.
It is well known that conventional sliders demonstrate flying height sensitivity to ambient pressure. Specifically, flying height is inversely proportional to operating altitude. Flying height sensitivity to ambient pressure poses severe problems for sliders that are designed to operate at very low flying heights (approximately 1 microinch), since a 20% drop in ambient pressure greatly increases the probability of contact between the slider and the disc surface.
This behavior forces disc drive designers to meet minimum flying height requirements at the highest specified altitude, which is typically 10,000 feet above sea level. As a result, the sliders are designed to fly with an undesirably large head-media spacing at altitudes where the disc drive is most frequently used, i.e., near sea level. Such a design compromise reduces the maximum useable linear density of the storage media and thus the storage capacity of the disc drive.
Improved sliders are desired which have a small flying height sensitivity to variations in ambient pressure.
One aspect of the present invention relates to a self-loading disc head slider having a slider body with leading and trailing slider edges, first and second side edges, and a length along a slider center line, from the leading slider edge to the trailing slider edge. First and second raised rails are positioned on the slider body, generally along the first and second side edges, respectively, and terminate prior to the trailing slider edge. The first and second raised rails form first and second bearing surfaces. A raised center pad is positioned along the trailing slider edge at the slider center line and forms a third bearing surface. A cavity dam is positioned rearward of the first and second raised rails and has a forward section, which is positioned forward of the raised center pad, and first and second leg sections, which extend rearward from the forward section on respective sides of the raised center pad. A subambient pressure cavity trails the cavity dam and extends on respective sides of the raised center pad.
Another aspect of the present invention relates to a self-loading disc head slider, which includes a slider body with leading and trailing slider edges and first and second side edges. First and second raised rails are positioned on the slider body, generally along the first and second side edges, respectively, and terminate prior to the trailing slider edge. A first cavity dam extends along the leading slider edge, between the first and second raised rails. A first subambient pressure cavity trails the first cavity dam, between the first and second raised rails. A second cavity dam is positioned rearward of the first and second raised rails. Third and fourth raised rails extends rearward from the second cavity dam, generally along the first and second side edges, respectively. A second subambient pressure cavity trails the second cavity dam. A raised center pad is positioned along the trailing slider edge.
Yet another aspect of the present invention relates to a disc drive assembly having a data storage disc, which is rotatable about an axis, and a slider for supporting a transducer at a flying height above the data storage disc during rotation of the data storage disc about the axis. The flying height is relatively insensitive to changes in altitude.